In the type of holder for hole saws where the holder is provided with an external thread on an axial holding stud, there is a problem upon replacement of hole saw by the fact that the use of the hole saw means that this is tightened hard in the thread and is then difficult to quickly replace by unscrewing it from the holding stud.
By U.S. Pat. No. 8,721,236, a holding device is previously known, which allows that a hole saw screwed onto a thread on a holder can be removed by displacing a friction means in the axial direction in relation to the holder to eliminate a preload of the thread. The position of the friction means of said holder device may be changed by means of an operating means, which is rotated in relation to the holder, which rotation gives rise to tangential motion of inner shoulders of the operating means. These shoulders press against balls situated in a gap between the friction means and the holder and are spring-biased by first spring means in the tangential direction. Furthermore, second spring means are connected to the holder to bias the balls in the radial direction. When the operating means is rotated, the balls are given a possibility of a radial movement by said second spring means, wherein the friction means may move in the direction from the hole saw and thereby eliminate the preload of the thread. The friction means is further, according to this known patent, rotationally fixed in relation to the holder.
This previously known holding device is complicated by it requiring two different types of springs, which act in different directions and one spring of which acts radially against the balls to press these outward when such a radial space is present. In addition, this construction is difficult to assemble because of its numerous components. Furthermore, there is greater risk of a complicated design that functional disorders will occur.
Such known designs are also bulky and require diameters that often are greater than the hole saw diameters, which implies that the holder will limit the possible depth of bore since the holder will be blocked by the workpiece.